Curtain wall assemblies comprising a series or ribbon of windows are well known. Typically, a series of frame members is erected to form a plurality of rectangular window openings. Window panes, or "lites," are then mounted to adjacent frame members over each of the window openings defined by the frame members. A retainer and weather seal, which may comprise different structures or a single unitary structure serving both functions, is used to affix the edges of the lite to the corresponding frame members. In a conventional glazing system, a retainer is attached to a first frame member. One edge of the lite is engaged with the retainer, and the opposite edge of the lite is brought into position against the second frame member. By reaching around the second frame member through the adjacent window opening, the installer then installs a second retainer onto the second frame member to secure and seal the second edge of the lite. The first edge of the next lite is then secured to the opposite side of the second retainer, and the windows are set in series.
In each ribbon of windows, there is one lite which is the last to be set. Unique problems are associated with the setting of the last lite. For example, the setting of other lites is somewhat simplified by the presence of the unoccupied window opening adjacent at least one side of the lite. The installer can reach through the unoccupied opening from within the building to perform those glazing steps which require access to the exterior side of the lite. However, the last lite is set in an opening which is enclosed on both sides by previously installed lites. Thus, certain glazing steps which are normally accomplished from the inside of the building by reaching through the adjoining window opening cannot be performed in this manner with respect to the last lite. Steps which require access to the exterior surface of the lite therefore require that certain aspects of the glazing procedure for the last lite be performed from outside the building. As will be appreciated, this requirement greatly complicates the erection sequence when the curtain wall is being installed on the upper floors of a multistory building. For example, scaffolding may have to be erected on the exterior of the building to provide a work platform from which to perform these exterior glazing steps.
Similar problems arise in the context of reglazing a lite. Irrespective of whether the replaced lite was originally the last lite glazed, the replacement lite is now being installed into an opening wherein both of the adjoining window openings are already glazed. Since access through the adjacent window openings is precluded, installation steps which require access to the exterior surface of the window, such as installation of a gasket, retainer, or weather seal, cannot be performed from inside the building. Replacing a lite on an upper floor of a multistory building is again greatly complicated and may require the erection of scaffolding or the like to replace the lite.
As used herein, the term "last lite" shall be understood to refer not only to the last lite to be set during the initial installation of a ribbon of windows but also to any lite which must be glazed when lites are already set in both of the adjoining window openings. Accordingly, a lite which is being replaced or reglazed when both adjoining window openings are already occupied by lites shall be understood to fall within the meaning of the term "last lite" as that term is used herein.
As will be appreciated, there is a need for a window glazing system which will facilitate installation of the last lite.
There is a further need for a window glazing system which will permit the last lite to be glazed entirely from within the interior of a building.